Why:
Another run of internal methods that should not be publicly
available from the base namespace.
This time the sequence involving methods were moved. It's worth noticing
that the ```Internal``` class is getting crowded. Maybe we can start
name-spacing the internal groups into modules under
```internal/sequence.rb``` ```internal/trait.rb``` and so on. Thoughts?
This PR:
- Moves the ```register_sequence```, ```sequence_by_name```,
```sequences``` and ```rewind_sequences``` to the
```FactoryBot::Internal``` module.
- Deprecates uses of ```sequence_by_name```, and ```sequences```
from the ```FactoryBot``` module.
- Refactor rewind sequences test to use spies
This is one of the steps towards fixing [this
issue](https://github.com/thoughtbot/factory_bot/pull/1285#1281)
5947e10578